Estimating Thickness of a Material Layer on an Aircraft

ABSTRACT

In some aspects, a wireless system is configured for estimating a thickness of a material layer on a surface of an aircraft. The wireless system includes a tag device located beneath a material layer. The tag device is capable of transmitting an electromagnetic signal in response to an electromagnetic signal. In some aspects, a transceiver device is configured to estimate the thickness of a material layer on a surface of an aircraft. The transceiver can be configured to communicate with a tag using electromagnetic signals. The transceiver can include one or more processors configured to measure signal strength and correlate the signal strength to the thickness of a material layer.

TECHNICAL FIELD

The following relates to estimating a thickness of a material layer onan aircraft.

BACKGROUND

A material layer on a surface of an aircraft can wear over time,reducing the thickness of the layer. In some cases it is desirable thatthe thickness of the material layer be monitored for safety orperformance reasons. The relevant part of the aircraft is typicallyremoved so that the layer thickness can be measured.

SUMMARY

This description relates to a wireless system for estimating thicknessof a material layer on an aircraft. In some aspects, a wireless systemis configured for estimating a thickness of a material layer on asurface of an aircraft. The wireless system includes a tag devicelocated beneath a material layer. The tag device is capable oftransmitting an electromagnetic signal in response to an electromagneticsignal. In some aspects, a transceiver device is configured to estimatethe thickness of a material layer on a surface of an aircraft. Thetransceiver can be configured to communicate with a tag usingelectromagnetic signals. The transceiver can include one or moreprocessors configured to measure signal strength and correlate thesignal strength to the thickness of a material layer.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic diagram of an example wireless thicknessestimation system.

FIG. 1B is a schematic diagram of an example wireless thicknessestimation system.

FIG. 2 is a schematic diagram of an example transceiver device.

FIG. 3 is an example plot diagram showing thickness measurements overtime.

FIG. 4A is an example diagram of tag locations on an aircraft.

FIG. 4B is an example diagram of tag locations on an aircraft.

FIG. 5 is a flow chart showing an example process for a wirelessthickness estimation system.

FIG. 6 is a schematic diagram of an example wireless thicknessestimation system including multiple tag devices.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1A and FIG. 1B are diagrams showing an example wireless system 100for estimating layer thickness. The example wireless system 100 includesa transceiver device 110 and a tag device 140. The tag device 140 islocated behind or beneath material layers 150, 160. The material layers150, 160 can be a coating, substrate, or other layer on a surface of anaircraft. For example, a material layer can be an erosion-resistantcoating such as epoxy-based carbon fiber and epoxy-based carbonnantotubes. The transceiver device 110 and the tag device 140 areconfigured to send and receive electromagnetic signals. For example, thetag device 140 can receive signals 120 sent by the transceiver device100, and the transceiver device 110 can receive signals 130 sent by thetag device 140.

The example tag device 140 can be a passive or active device such as aRadio Frequency Identification (RFID) tag. In some cases, the tag device140 is configured to send a signal 130 in response to receiving a signal120. The electromagnetic signal 130 can include identification data,location data, status data, or other information. The electromagneticsignals 120, 130 can be any electromagnetic signal, with frequenciesincluding radio frequency, high frequency, ultra-high frequency or otherfrequencies. In some cases, the electromagnetic signals 120, 130 includemultiple frequencies or frequency ranges. The electromagnetic signals120, 130 can be transmitted through the material layers 150, 160. Thematerial layers 150, 160 can be one or more coatings or layers on asurface of an aircraft or aircraft part. For example, one or more oflayers 150, 160 can be a sacrificial layer on a rotor blade of avertical lift aircraft.

The example transceiver device 110 can be a handheld or portable device,or be a component incorporated into a separate device. The transceiverdevice 110 can be configured to process received signals 130. Forexample, the transceiver device 110 can contain one or more modules thatanalyze the strength of the signal 130 and correlate the signal strengthto material or structural properties (e.g., layer thickness). In someimplementations, the transceiver device 110 includes a display thatpresents the material or structural properties. For example, thetransceiver device 110 could display the estimated thickness of amaterial layer. In some implementations, the transceiver device 110communicates with a separate computer or display via wired or wirelessconnection.

FIG. 1A depicts the wireless system 100 in an example in which thematerial layers 150, 160 are at their full thickness. For example, ifmaterial layer 160 is a coating, FIG. 1A shows a new material layer 160immediately after application. The tag device 140 is located beneath thelayers 150, 160, and transmits a signal 130 through the layers 150, 160in response to receiving a signal 120 from transceiver device 110. Thesignal 130 is attenuated by reflection or absorption during propagationthrough the material layers 150, 160. The material layers 150, 160 maybe plastics, composites, metals, natural fiber materials, epoxy-basedcarbon fiber, epoxy-based carbon nantotubes, or other materials.

FIG. 1B depicts the wireless system 100 of FIG. 1A at a later time inwhich material layer 160 has eroded, abraded, corroded, or otherwisediminished, reducing the thickness. For example, friction during use canwear a coating on the external surface of an aircraft. In FIG. 1B, thesignal 130 transmitted by the tag device 150 is less attenuated (i.e. isstronger) because the material layer 160 is thinner. A thinner materiallayer 160 can reflect or absorb less of the electromagnetic signal 130.The transceiver device 110 can compare the original attenuated strengthfrom signal 130 shown in FIG. 1A with the less attenuated strength shownin FIG. 1B. Based on the comparison between signal strengths, thetransceiver device 110 can estimate the thickness of layer 160 that hasbeen lost to erosion or abrasion. If the signal strength through a fullthickness (e.g. FIG. 1A) is known, then the remaining thickness of thelayer can be calculated or otherwise estimated.

FIG. 2 is a schematic diagram showing an example transceiver device 210,such as the transceiver device 110 shown in FIG. 1. The transceiverdevice 210 includes a transceiver 212 that wirelessly communicates usingan antenna 214. The transceiver device 210 also includes one or moreprocessors 216. Example processors include a read module 218 and anevaluation module 220. The transceiver device 210 also includes a memorymodule 222, configured to store one or more documents 224. Thecomponents in the example transceiver device 210 can be connected orotherwise communicate with each other. For example, the evaluationmodule 220 could access or manipulate data stored in the memory module222. The components can also be located in a separate device, such as aseparate computer. For example, the evaluation module 220 could belocated in a separate computer that communicates with the transceiverdevice 210 via a wired or wireless connection.

The example transceiver 212 is connected to the antenna 214. Thetransceiver 212 is configured to send and receive electromagneticsignals via the antenna 214. For example, the transceiver 212 can sendan electromagnetic signal (e.g., a radio-frequency transmission or ahigh-frequency transmission) to a tag device. The transceiver 212 canalso receive an electromagnetic signal from a device such as a tagdevice.

The example processors 216 can be implemented within the transceiverdevice 210. The processors 216 can include one or more software orhardware modules. The example read module 218 is a software or hardwaremodule configured to process the signal received from a tag device. Forexample, the read module 218 could determine identification data fromthe signal or the signal strength. The example evaluation module 220 isa software or hardware module configured to process the information fromthe read module 218. In some cases, the evaluation module 220 can alsoaccess other modules, such as information stored in the memory 222. Theevaluation module 220 can be configured to process the information withan algorithm, for example an algorithm to perform statistical analysison some or all the information, including forecasting a trend. In somecases, the evaluation module 220 is configured to calculate an estimatedlayer thickness based on the strength of the signal received from a tagdevice.

The example memory module 222 includes documents 224. The documents 224can be files containing information. For example, the documents 224 cancontain data received from the processors 216. The documents 224 cancontain other information, such as log data, tag identification data,estimated thickness data, or tables or lists of data.

The transceiver device 210 can also include other modules or components.For example, the transceiver device 210 may include a display. Thetransceiver device 210 may also include a sensor to detect when thetransceiver device 210 is properly positioned over a tag device. Whenthe transceiver device is properly positioned over a tag device, anaudible alarm could sound or a message could appear on a display. Thetransceiver device 210 could also include modules for communicating withover devices, such as over a wireless connection or over a wiredconnection.

FIG. 3 shows an example diagram 300 of estimated thicknesses of amaterial layer over time. The estimated thicknesses can be determinedusing the wireless system of FIG. 1. In diagram 300, individualestimations of layer thickness are shown at points 310 a, 310 b, 310 c,310 d, and 310 e. Each point 310 a, 310 b, 310 c, 310 d, and 310 erepresents a measurement of estimated thickness taken at a certain time.The points 310 a, 310 b, 310 c, 310 d, 310 e are representative, andmore or fewer points can be acquired or analyzed. In diagram 300, thex-axis represents the time each measurement is taken. The time scale canbe any appropriate time scale such as days, months, or years. In somecases, the time scale can represent other values such as the number offlights or the cumulative flight time (e.g., in hours) of an aircraft.In some cases, a threshold thickness 320 can be specified. For example,if the measured layer thickness is less than the threshold thickness320, the user may be notified that the layer should be replaced orrepaired.

The point 310 a can represent the first layer thickness measurement of aset of measurements. In some cases, point 310 a can represent theestimated thickness of a layer that is new and not eroded. As thematerial layer erodes over time, each subsequent measurement ofestimated thickness (i.e., points 310 b, 310 c, 310 d, 310 e) can be asmaller value. In some cases, these points can show a trend ofdecreasing thickness over time. Statistical analysis of the points (e.g.trend forecasting) can generate an estimation of the time 330 the layerthickness will erode to the threshold thickness 320. Thus, the part orlayer can be replaced or repaired approximately at or before the layerthickness erodes beyond the threshold thickness 320.

FIGS. 4A and 4B are illustrations of example aircraft with examplelocations for a wireless thickness estimation system. FIG. 4A is anillustration of an example aircraft 400. Example locations on aircraft400 include a windshield 402, a radome 404, a turbine engine blade 406,or a wing 408. FIG. 4B is an illustration of an example vertical liftaircraft 450. Example locations on vertical lift aircraft 450 includewindshield 452 and rotor blade 454. A wireless thickness estimationsystem can be used on these or other locations. For example, one or moretag devices could be located beneath the outer surface of radome 404. Insome cases, one or more markings can be present on the surface to showthe location of a tag device. For example, a visible dot or crosshairscan be located on the surface to indicate a tag device beneath.

FIG. 5 is a flow chart diagram of example wireless thickness estimationprocess 300. The example wireless thickness estimation process 500 is aprocess to estimate the thickness of a material layer on a surface of anaircraft or aircraft part. The example process 500 can be based on thewireless system described in FIG. 1.

At 502, the wireless system is calibrated. For calibration, thethickness of a new material layer can be estimated using, for example,the transceiver device 200 of FIG. 2 and logged for comparison withsubsequent measurements of that layer. The calibration can also be usedto verify the wireless system is working properly if the thickness of anew layer is known. Alternately or in combination, the calibration couldbe used to verify that a new layer has a thickness within a specifiedtolerance. In other instances, a layer that is not new (i.e. has erodedsome amount) can be used for calibration.

At 504, the material layer corrodes or erodes. For example, the materiallayer can erode during use (e.g. in flight), decreasing the thickness ofthe layer. At 506, the signal strength is measured using, for example,the transceiver device 200.

At 508, the measured signal strength is correlated to an estimation ofthe thickness of the material layer. In some instances, the thickness isestimated by calculating from the signal strength based on an algorithm.In some instances, the thickness can be estimated using a table lookupidentifying thickness values correlated with signal strength values.

At 510, the approximate time until the layer has reached a thresholdthickness is calculated. The threshold thickness can be a thresholdspecified for that specific material layer, that specific aircraft part,or that location on the layer or part. The approximate time can becalculated using an algorithm or statistical techniques. The approximatetime can be calculated based on one or more thickness measurements.

At 512, the approximate time calculated at 510 is above some set timethreshold (e.g. within some number of hours of operation), or the layerhas not eroded sufficiently to warrant repair or replacement. Thus, thepart or surface can be used until a subsequent measurement is taken. Ifthe approximate time calculated at 510 is at or below some set timethreshold, the part or layer can be repaired or replaced (at 514). Insome implementations, the estimated thickness is compared directly withthe threshold thickness, and an approximate time is not calculated or isunused.

FIG. 6 shows an example wireless thickness estimation system 600. Theexample wireless system 600 is substantially similar to the wirelesssystem 100. In wireless system 600, the example transceiver device 610is able to communicate with multiple example tag devices 640 a, 640 b,and 640 c that are located beneath a material layer 650. In someimplementations, more or fewer tag devices are used, and the tag devicescan be in any configuration or distribution. The transceiver 610 cansend a signal 620 that is received by the multiple tag devices 640 a,640 b, 640 c. The tag devices 640 a, 640 b, 640 c can send signals 630a, 630 b, 630 c, respectively, that are received by the transceiver 610.

In some cases, the wireless thickness estimation system 600 can be usedto take a single measurement of material layer 650 using multiple tagdevices 640 a, 640 b, 640 c. In this situation, the transceiver device610 does not have to be located directly opposite a tag device. Thetransceiver device 610 can use an algorithm to compute the thickness ofmaterial layer 650 based on the signal strength of signals 630 a, 630 b,630 c and other signal information (e.g. tag identification signals)received from tag devices 640 a, 640 b, 640 c. For example, thetransceiver device 610 can triangulate its location relative to one ormore tag devices 640 a, 640 b, 640 c. The transceiver device 610 canthen compensate for tag device location when calculating the thicknessof material layer 650. In some cases, multiple signals can be processedto determine an average material layer thickness. In some cases, thelocations or distribution of tag devices is known, and a thicknessestimation algorithm that the transceiver device 610 uses can be basedon these known locations.

The wireless thickness estimation system described herein could also beused to monitor the thickness of a layer as the thickness increases. Insome implementations, a tag device could be located beneath a layer orpart upon which a residue accumulates over time. In this manner, thethickness of residue could be monitored and the part could be cleaned,repaired, or replaced if the accumulated thickness exceeds somethreshold.

The wireless thickness estimation system described herein does notnecessitate the removal of the part or component. Removing a part toevaluate the thickness of a layer on the part can be expensive andtime-consuming. The wireless thickness estimation system enables ameasurement of wear or damage to be determined instantly withoutdisassembly. The wireless system can also predict when a material layerapproaches a threshold thickness, so the material layer can be replacedor repaired when pass the threshold thickness. The wireless system canbe used on stationary components or moving components. The tag devicescan be placed or buried beneath any thickness of material layer. Thematerial layers can include materials such as plastics, composites,metals, natural fiber materials, or other materials. The tag devices canbe passive devices that do or do not have a battery and that activatesto broadcast signals when turned on, or the tag devices can be activedevices that broadcast signals at all times. The tag devices can also below-profile devices that do not add appreciable weight or thickness toparts or surfaces.

While this specification contains many details, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features specific to particular examples. Certainfeatures that are described in this specification in the context ofseparate implementations can also be combined. Conversely, variousfeatures that are described in the context of a single implementationcan also be implemented in multiple embodiments separately or in anysuitable subcombination.

A number of examples have been described. Nevertheless, it will beunderstood that various modifications can be made. Accordingly, otherimplementations are within the scope of the following claims.

1. A wireless system for estimating a thickness of a material layeradjacent a surface of an aircraft component, comprising: a tag devicelocated between a portion of a surface of an aircraft component and amaterial layer adjacent to and touching the surface of the aircraftcomponent, the tag device capable of wireless communication with atransceiver, the tag device configured to transmit a wireless signalthrough the material layer; a transceiver configured to wirelesslycommunicate with the tag device, receive the wireless signal from thetag device, and compensate a signal strength of the wireless signalbased on a location of the transceiver relative to the tag device,wherein the signal strength of the wireless signal received by thetransceiver from the tag device varies with a thickness of the materiallayer; and wherein one or more processors of the transceiver areconfigured to measure the compensated signal strength of the wirelesssignal and correlate the compensated signal strength to a thickness of amaterial layer.
 2. The wireless system of claim 1, wherein the tagdevice wireless communicates using an electromagnetic signal, and theelectromagnetic signal includes at least one of a radio frequencysignal, a high-frequency signal, an ultra-high-frequency signals, asignal having a frequency lower than radio frequency, or a signal havinga frequency higher than ultra-high-frequency.
 3. The wireless system ofclaim 1, wherein the tag device is an RFID device.
 4. The wirelesssystem of claim 1, wherein the tag device is a passive device.
 5. Thewireless system of claim 1, wherein the tag device is an active device.6. The wireless system of claim 1, wherein the material layer comprisesa sacrificial layer touching the surface of the aircraft component, andwherein the tag device is positioned between the sacrificial layer andthe surface of the aircraft component.
 7. The wireless system of claim1, wherein the aircraft component comprises a rotor blade on a verticallife aircraft, a blade of a turbine engine, a radome of an aircraft, awing of an aircraft, or a windshield of an aircraft.
 8. (canceled) 9.(canceled)
 10. (canceled)
 11. (canceled)
 12. (canceled)
 13. (canceled)14. (canceled)
 15. A method for estimating a thickness of a materiallayer on a surface of an aircraft component, the method comprising:placing a material layer over a surface of an aircraft component, thematerial layer contacting the aircraft component; positioning a tagdevice between the surface of the aircraft component and the materiallayer; transmitting, to the tag device and from a transceiver, a firstwireless signal; receiving, at the transceiver, a second wireless signaltransmitted through the material layer from the tag device; determininga location of the transceiver relative to the tag device; determining asignal strength of the second wireless signal; and correlating thesignal strength to a thickness of the material layer to estimate a firstthickness of the material layer, wherein the transceiver compensates forthe determined location of the transceiver relative to the tag device.16. The method of claim 15, wherein the tag device wirelesslycommunicates using an electromagnetic signal, and the electromagneticsignal includes at least one of a radio frequency signal, ahigh-frequency signal, an ultra-high-frequency signals, a signal havinga frequency lower than radio frequency, or a signal having a frequencyhigher than ultra-high-frequency.
 17. The method of claim 15, whereinthe tag device is an RFID device.
 18. The method of claim 15, whereinthe tag device is a passive device or an active device.
 19. The methodof claim 15, wherein the material layer comprises a sacrificial layertouching the surface of the aircraft component, and wherein the tagdevice is positioned between the sacrificial layer and the surface ofthe aircraft component.
 20. The method of claim 15, wherein the aircraftcomponent comprises a rotor blade on a vertical life aircraft, a bladeof a turbine engine, a radome of an aircraft, a wing of an aircraft, ora windshield of an aircraft.
 21. The method of claim 15, whereincorrelating the signal strength to the thickness of the material layercomprises determining that the thickness of the material layer hasincreased over time.
 22. The method of claim 15, wherein the thicknessis a first thickness estimated at a first time instant, and wherein themethod further comprises: estimating, at a second time instant after thefirst time instant, a second thickness of the material layer, the secondthickness less than the first thickness due to an erosion of thematerial layer; and estimating, based on the first thickness, the secondthickness, the first time and the second time, a time for the thicknessof the material layer to erode to a threshold thickness for the materiallayer.
 23. The method of claim 22, wherein estimating, at the secondtime instant after the first time instant, the second thickness of thematerial layer, comprises: transmitting, to the tag device and at thesecond time instant, a third wireless signal; receiving a fourthwireless signal from the tag device; determining a signal strength ofthe fourth wireless signal; and correlating the signal strength of thefourth wireless signal to the second thickness of the material layer.24. A method for estimating a thickness of a material layer on a surfaceof an aircraft component, the method comprising: placing a materiallayer over a surface of an aircraft component, the material layercontacting the aircraft component; placing a plurality of tag devicesbetween the surface of the aircraft component and the material layer,each tag device separated from an adjacent tag device by a distancealong the surface of the aircraft component; transmitting, from atransceiver, a wireless signal to the plurality of tag devices;receiving, at the transceiver, a plurality of wireless signal responses,each wireless signal response generated and transmitted by acorresponding tag device of the plurality of tag devices in response tothe wireless signal transmitted from the transceiver, wherein eachwireless signal response comprises tag identification information of acorresponding tag device of the plurality of tag devices; measuring,with the transceiver, a signal strength of each wireless signal responsefrom the corresponding tag device; determining a location of thetransceiver relative to the plurality of tag devices based on the signalstrengths of the wireless signal responses and the tag identificationinformation from the plurality of tag devices; and determining athickness of the material layer based on the signal strengths of theplurality of wireless signal responses and the tag identificationinformation from the plurality of tag devices, wherein the location ofthe transceiver relative to the tag devices is compensated for whendetermining the thickness of the material layer.
 25. The method of claim24, wherein determining a location of the transceiver comprisestriangulating, by the transceiver, a location of the transceiverrelative to the plurality of tag devices.